If the potatoes are large, cut into equal chunks about the size of golf balls. Place in a single layer in a microwaveable dish. Cover with waxed paper. Microwave on high for about 10 minutes, rotating occasionally until tender.

Remove and set aside for 10 minutes or until cool enough to handle.

In a bowl, whisk the pesto, mayonnaise, 1 tablespoon olive oil, salt and black pepper. Add the scallions. Cut the potatoes into ½-inch chunks and add to the bowl. Toss. Add up to 1 tablespoon more olive oil if needed.